1. Field of the Invention
The present invention relates to an image processing device and an image processing method which perform a dynamic range compression process for an image such as a radiological image.
2. Description of the Related Art
A radiological image used in an image diagnosis is acquired by an imaging process of a computed radiography (CR) system or an imaging process using a radiation detector (FPD). The dynamic range of the acquired radiological image is very wide. In a case in which an output device reproduces the radiological image with a wide dynamic range, the dynamic range of the image is compressed so as to fall within a concentration range which can be output by the output device, in order to prevent the occurrence of blown-out highlights in a bright portion of the image and the occurrence of blocked-up shadows in a dark portion of the image. For example, JP2000-155838A discloses a method which sets the concentration range (latitude; hereinafter, referred to as an L value) of an image to which a range from the minimum value to the maximum value of the concentration scale of an output device is allocated, sets the concentration range of a region of interest which is included in the image and is to be observed as a concentration range which is not subjected to a dynamic range compression process, and calculates dynamic range compression parameters (for example, a compression table) on the basis of the set concentration ranges. JP2003-310589A discloses a method which changes dynamic range compression parameters, depending on at least one of information about the dynamic range of a subject and information about a captured part of the subject.
JP2013-138913A discloses a method which, when dynamic range compression parameters are set and the gradient of gradation is corrected, corrects a concentration range for compressing the dynamic range according to the corrected gradation.